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Title:
PANEL FOR VEHICLE COMPRISING A COATED STEEL SHEET LOCALLY REINFORCED
Document Type and Number:
WIPO Patent Application WO/2016/156896
Kind Code:
A1
Abstract:
The present invention relates to a panel for vehicle comprising a coated steel sheet locally reinforced, a method for preparing the panel and the use of the panel.

Inventors:
DOSDAT LAURENCE (FR)
AMBLARD MATTHIEU (FR)
Application Number:
PCT/IB2015/000422
Publication Date:
October 06, 2016
Filing Date:
March 31, 2015
Export Citation:
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Assignee:
ARCELORMITTAL (LU)
International Classes:
C23C28/00; B60J5/04; C23C2/26; C23C30/00
Foreign References:
US4399174A1983-08-16
Other References:
"NITOHARD SERIES STRUCTURAL REINFORCEMENT PATCH", 11 July 2013 (2013-07-11), XP055191746, Retrieved from the Internet [retrieved on 20150528]
N. LEBOZEC ET AL: "Corrosion performance of Zn-Mg-Al coated steel in accelerated corrosion tests used in the automotive industry and field exposures", MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, vol. 64, no. 11, 11 March 2013 (2013-03-11), pages 969 - 978, XP055191748, ISSN: 0947-5117, DOI: 10.1002/maco.201206959
MARGOT VLOT ET AL: "Magizinc (ZnAIMg) Coatings versus galvannealed Authors MAGIZINC (ZnAlMg) COATINGS VERSUS GALVANNEALED", 4 May 2011 (2011-05-04), XP055191751, Retrieved from the Internet [retrieved on 20150528]
"Bake-hardening steels BHZ", 1 June 2013 (2013-06-01), XP055191755, Retrieved from the Internet [retrieved on 20150528]
"Zagnelis(TM) -Double-sided ZnMgAl galvanized steels", 5 July 2013 (2013-07-05), XP055191758, Retrieved from the Internet [retrieved on 20150528]
None
Attorney, Agent or Firm:
PLAISANT, Sophie (Research & Development Intellectual Property, rue Andre Campra La Plaine Saint Denis, FR)
Download PDF:
Claims:
CLAIMS

Panel for vehicle comprising a steel sheet (1 ) having one outer face (1 a) and one inner face (1 b), wherein at least the inner face is coated with a coating (2) comprising from 1.0 to 6.0 % by weight of aluminum, from 0.5 to 5.0 % by weight of magnesium, the balance being zinc and optionally impurities and optionally additional elements chosen from Si, Sb, Pb, Ti, Ca, Mn, Sn, La, Ce, Cr, Zr or Bi, the content by weight of each additional element being inferior to 0.3% by weight, said sheet being locally reinforced by at least one patch (3) bound to said inner face ( b).

Panel according to claim 1 , wherein the coating (2) comprises from 1 .0 to 1.4 % by weight of aluminum, from 1.0 to 1 .4 % by weight of magnesium, the balance being zinc and optionally impurities and optionally additional elements chosen from Si, Sb, Pb, Ti, Ca, Mn, Sn, La, Ce, Cr, Zr or Bi, the content by weight of each additional element being inferior to 0.3% by weight.

Panel according to claim 1 , wherein the coating (2) comprises from 3.5 to 3.9 % by weight of aluminum, from 2.3 to 3.3 % by weight of magnesium, the balance being zinc and optionally impurities and optionally additional elements chosen from Si, Sb, Pb, Ti, Ca, Mn, Sn, La, Ce, Cr, Zr or Bi, the content by weight of each additional element being inferior to 0.3% by weight.

Panel according to anyone of claims 1 to 3, wherein the patch comprises a resin layer (3a) and an inorganic material layer (3b), said resin layer being in contact with the coating (2) of the inner face. Panel according to claim 4, wherein the resin layer (3a) has a young's modulus between 1 and 200 MPa and the inorganic layer (3b) has a young's modulus between 1 and 15 GPa.

Panel according to claims 4 or 5, wherein said inorganic material layer (3b) is made of glass fiber and said resin layer (3a) is a foam material.

Panel according to claim 6, wherein said resin layer (3a) is an epoxy- rubber based material.

Panel according to anyone of claims 4 to 7, wherein the resin layer (3a) is made of sticky material.

Panel according to anyone of claims 1 to 8, wherein said outer face (1a) and inner face (1b) further comprise a phosphate layer (4) and an e-coating layer (5).

Panel according to anyone of claims 1 to 9, being a dash panel, an interior door panel, an exterior door panel, a roof panel, a wheel arch, a vehicle floor, an interior hood panel, an exterior hood panel, a fender or a body side of a vehicle.

Panel according to claims 1 to 10, wherein the steel sheet has a thickness between 0.4 to 1.0 mm.

Panel according to claims 1 to 11 , wherein the steel sheet has thickness between 0.5 to 0.7 mm.

A method for preparing a panel for vehicle comprising the following steps:

A) the provision of a steel sheet having at least the inner face coated with a coating comprising from 1.0 to 6.0 % by weight of aluminum, from 0.5 to 5.0 % by weight of magnesium, the balance being zinc and optionally impurities and optionally additional elements chosen from Si, Sb, Pb, Ti, Ca, Mn, Sn, La, Ce, Cr, Zr or Bi, the content by weight of each additional element being inferior to 0.3% by weight,

B) the application of at least one patch onto the coated steel sheet obtained from step A),

C) the stamping, said stamping being before or after step B),

D) a phosphating step and

E) an e-coating step. 14. A method according to claim 13, wherein the coated steel sheet is cut before or after step B) or before, during or after step C).

15. A method according to claim 13 or 14, wherein during step B), the patch is stuck on the coated sheet sheet.

16. A method according to anyone of claims 13 to 15, wherein the step E) is performed in an oven at a temperature between 160 and 180°C during 20 to 35 minutes. 17. Use of a panel according to anyone of claims 1 to 12, or obtainable according to the method of anyone of claims 13 to 16, for the manufacture of a part of automotive vehicle.

Description:
Panel for vehicle comprising a coated steel sheet locally reinforced

The present invention relates to a panel for vehicle comprising a coated steel sheet, said steel sheet being locally reinforced by a patch. The invention is particularly well suited for the manufacture of parts of automotives vehicles.

With a view of saving the weight of vehicles, it is known to reinforce locally steel sheets by adding a patch. Thus, the weight of the steel sheet, i.e, the thickness, decreases and the local addition of a patch allows for a high strength. The steel sheets are generally coated with a metal coating. Then, the panels comprising the coated steel sheet are painted. However, in practice, it was observed that the known metallic coatings may be prone to delamination issues of paint layers around the patch.

Indeed, water infiltrates between paint layers, for example e-coating layer, and the edges of the patch. Thus, corrosion products are formed under the paint player resulting in the delamination of paint layers around the patch.

The object of the invention is to provide a panel for vehicle locally reinforced with at least one patch which does not have delamination issues around the patch.

This object is achieved by providing a panel for vehicle locally reinforced according to claim 1. The panel can also comprise characteristics of claims 2 to 12.

The second object is achieved by providing a process for preparing a panel for vehicle according to claim 13. The process can also comprise characteristics of claims 14 to 16.

The third object is achieved by providing the use of the panel for the manufacture of a part of an automotive vehicle according to claim 17.

Other characteristics and advantages of the invention will become apparent from the following detailed description of the invention,

To illustrate the invention, various embodiments and trials of non limiting examples will be described, particularly with reference to the following Figures: Figure 1 is a schematic representation of one embodiment according to the invention.

Figure 2 is a schematic representation of another embodiment according to the invention.

Figure 3 is a schematic representation of a door of a vehicle according to the invention.

In all figures, the layer thickness shown is given by way of illustration and can not be considered as a scale representation of the layers.

The invention relates to a panel for vehicle comprising a steel sheet 1 having one outer face 1a and one inner face 1 b. Figure 1 shows one embodiment wherein the inner face is coated with a coating 2 comprising from 1.0 to 6.0 % by weight of aluminum, from 0.5 to 5.0 % by weight of magnesium, preferably from 1.0 to 5.0% by weight of magnesium, the balance being zinc and optionally impurities and optionally additional elements chosen from Si, Sb, Pb, Ti, Ca, Mn, Sn, La, Ce, Cr, Zr or Bi, the content by weight of each additional element being inferior to 0.3% by weight, said sheet being locally reinforced by at least one patch 3 bound to said inner face 1 b. Preferably, the coating according to the invention is deposited on the inner face and the outer face of the steel sheet.

Advantageously, the coating comprises from 1.0 to 1.4 % by weight of aluminum, from 1.0 to 1.4 % by weight of magnesium, the balance being zinc.

In another preferred embodiment, the coating comprises from 3.5 to 3.9 % by weight of aluminum, from 2.3 to 3.3 % by weight of magnesium, the balance being zinc.

The coating can be deposited by any methods known to the man skilled in the art, for example hot-dip galvanization process. In this process, the steel sheet for example obtained by hot and cold rolling is dipped in a molten metal bath.

The bath comprises zinc, magnesium and aluminum. It can comprise additional elements chosen from Si, Sb, Pb, Ti, Ca, Mn, Sn, La, Ce, Cr, Zr or Bi. These additional elements can improve among others ductibility, coating adhesion on the steel sheet. The bath can also contain impurities from feeding ingots or from the passage of the steel sheet in the molten bath, such as iron with a content up to 0.5% by weight, and usually between 0.1 et 0.4% by weight.

The bath temperature is between 360 and 480°C, preferably 420 and 460°C. The thickness of the coating is usually inferior or equal to 25μηι.

After the deposition of the coating, the steel sheet is for example wiped with nozzles ejecting gas on both sides of the coated steel sheet. The coated steel sheet is then cooled. When only the inner face is coated, a brushing is realized to take off the coating deposited on the outer face.

Preferably, the cooling rate is superior or equal to 15°C.s "1 between the beginning of the solidification and the end of the solidification. Advantageously, the cooling rate between the beginning and the end of the solidification is superior or equal to 20°C.s "1 .

Then, a skin-pass can be realized and allows work hardening the coated steel sheet and giving it a roughness facilitating the subsequent shaping. A degreasing and a surface treatment can be applied in order to improve for example adhesive bonding or corrosion resistance.

The coated steel sheet is then cut. In other embodiments, the coated steel sheet is cut after the application of the patch or before, during or after the stamping.

According to the invention, the panel, comprising the coated steel sheet, is such that the steel sheet is locally reinforced by at least one patch bound to the inner face of the steel sheet. For example, the patch can comprise a resin layer 3a and an inorganic material layer 3b, said resin layer being in contact with the coating of the inner face.

Preferably, the inorganic material is made of glass fiber. The resin layer is preferably a foam material, for example an epoxy-rubber based material. Advantageously, the resin layer is made of sticky material. Thus, the patch is preferably stuck on the inner face of the steel sheet in order to locally reinforce the sheet. For example, the patch is Nitohard®.

In a preferred embodiment, the resin layer has a young's modulus between 1 and 200 MPa and the inorganic layer has a young's modulus between 1 and 15 GPa. Without wishing to be bound by any theory, it has been found that when youngs moduli are superior to these values, there is a greater risk that the patch creates a surface defect. When youngs moduli are inferior to these values, there is a risk that the reinforcement strength of the patch decreases.

In another embodiment, the patch comprises a resin layer, preferably a foam material, said resin layer being reinforced by an inorganic material. For example, the inorganic material is made of glass fiber or carbon fiber.

A stamping of the panel is realized before or after the bonding of the patch. Preferably, the stamping is realized before by any methods known to the man skilled in the art, for example for the outer panel.

Figure 2 illustrates a panel according to the invention having a phosphate layer 4 and an e-coating layer 5, said panel comprising a steel sheet coated with the coating according to the invention on both faces. At this end, a phosphating step and an e-coating step are successively realized.

The phosphating, which improves the paint adhesion, is realized by any method known to the man skilled in the art. Usually, the thickness of the phosphate layer is between 1 and 2 pm.

The e-coating step is realized by dipping the panel into a bath comprising for example an aqueous solution comprising Pigment paste® W9712-N6 and Resin blend® W791 1 -N6 from PPG Industries during 120 to 180 seconds at a temperature between 28 and 35°C. The pH of the solution is preferably between 5.5 and 5.8. A current between 200 and 320°C is applied. Then, the panel is wiped and cured in the oven at a temperature between 160 and 180°C during 20 to 35 minutes. During the curing, the resin layer of the patch is foamed and hardened. Usually, the thickness of the e- coating layer is between 15 and 25pm, preferably inferior or equal to 20pm.

After the e-coating step, other paint layers can be deposited, for example, a primer coat of paint, a basecoat layer and a top coat layer.

A panel locally reinforced comprising a coated steel sheet according to the invention is thus obtained. The weight saving is huge since it allows for a panel wherein the steel sheet has for example a thickness between 0.4 to .0 mm, preferably 0.5 to 0.7mm.

The panel according to the invention can be a dash panel, an interior door panel, an exterior door panel, a roof panel, a wheel arch, a vehicle floor, an interior hood panel, an exterior hood panel, a fender or a body side of a vehicle.

Figure 3 illustrates a door of vehicle comprising an exterior door panel A and an interior door panel B. The exterior door panel comprising a coated steel sheet is locally reinforced with a patch 3 according to the present invention. The interior door panel can be coated with a coating according to the invention or a zinc coating. Zinc coating can be deposited by any method known to the man skilled in the art, for example by hot-dip galvanization process or electrogalvanization.

The door panel is a part of the vehicle very subjected to delamination issues of paint layers around the patch. Indeed, water present on the vehicle glass infiltrates inside of the door, i.e. between the interior and exterior door panel. In contrary to known metallic coatings, the panel according to the invention allows for a high resistance to delamination around the patch.

Additionally, there is an important risk that the patch creates a surface defect on a coated panel due to the weak thickness of the panel. Specifically in the case of outer panel, users can realized a test consisting in viewing the panel in a neon room in order to verify the quality of the surface aspect. At this end, the panel can be covered with an oil film to increase its reflectivity, and is placed under a ramp of parallel neon lights. The surface defects are well highlighted by irregularities of reflection of light strips.

With a panel according to the present invention, there is a good surface aspect, i.e. no surface defect even under neon lights, which is an important criteria for users.

The invention will now be explained in trials carried out for information only. They are not limiting.

Examples

For all trials, steel sheets used are 180BH® and IF220®. The composition of the steel 180BH® is as follows : C=0.0016%, S=0.01 1 %, N=0.0025%, Mn=0.2%, P=0.014%, Si=0.044%, Cu=0.033%, Ni=0.015%, Cr=0.026%, Al=0.032%, As=0.002%, Mo=0.004%, V=0.002%, Sn=0.0025%, Nb=0.007%, Ti=0.001 %, B=0.0028%, Zr<0.003%. Panel according to the present invention and various panels were prepared and subjected to a delamination test.

Trials 1 , 2 and 3 are panels according to the present invention. These panels comprise steel sheets coated with a coating comprising 3.7% by weight of aluminum and 3% by weight of magnesium, the balance being zinc. In trials 1 , 2 and 3, the thickness of the coating is respectively of 6pm, 7.5pm and 10pm. The coating was deposited by hot-dip galvanization process.

Trial 4 is a comparative panel comprising a steel sheet coated with a zinc coating. The zinc coating, having a thickness of 7.5pm, was deposited by hot dip galvanization process.

Trial 5 is another comparative panel comprising a steel sheet coated with a zinc coating. The zinc coating, having a thickness of 7.5pm, was deposited by electrogalvanization process.

For all trials, the coated steel sheet was cut and then stamped. After, a patch Nitohard® RE-2000 was stuck onto the coated steel sheet. It was followed by a phosphating step realized by dipping into a bath comprising a solution of Gardobond® 24 TA, Gardobond® Add H7141 , Gardobond® H7 02, Gardobond® Add H7257, Gardobond® Add H7101 , Gardobond® Add H7155 during 3 minutes at 50°C. The panel was then wiped with water and dried with hot air.

An e-coating layer of 20pm was deposited the phosphate layer. At this end, all trials were dipped into a bath comprising an aqueous solution comprising Pigment paste® W9712-N6 and Resin blend® W7911 -N6 of PPG Industries during 180 seconds at 30°C. A 200V current was applied. Then, the panel was wiped and cured in the oven at 180°C during 35 minutes.

A test, consisting in submitting panels to corrosion cycles according to the norm VDA 233-102, was then realized. Trials were put in a chamber wherein an aqueous solution of sodium chloride of 1 % by weight was vaporized on trials with a rate of flow of 3mL.h "1 . The temperature varied from 50 to -15°C and the humidity rate varied from 50 to 100%. Figures 4 illustrates one cycle corresponding to 168 hours, i.e. one week.

The presence of delamination around the patch was observed by naked eyes: 0 means excellent, in other words, there is little or no delamination around the patch and 5 means very bad, in other words, there are lots of delamination around the patch.

The panel according to the invention leads to no or little delamination around the patch, even after 25 weeks of corrosion cycle, in contrary to the panel comprising a zinc coated steel sheet.